The present invention relates to a scroll fluid machine such as a scroll vacuum pump or a scroll compressor, and particularly to a scroll fluid machine comprising a fixed scroll having a fixed wrap in a housing and an orbiting scroll having an orbiting wrap, said orbiting scroll being eccentrically revolved with a driving shaft via an eccentric axial portion so that a gas sucked from the outer circumference or a center may be compressed or decompressed towards the center or outer circumference respectively.
Such a scroll fluid machine is well-known among persons skilled in the art as described in a number of references such as JP7-42953B2 and JP10-26090A.
In such a scroll fluid machine, long operation time raises the temperatures of an axial end portion of a driving shaft, a bearing or a packing that support it, end plates of wraps of fixed and orbiting scrolls, a tip seal that engages with the tip end of the wrap and a motor, causing excessive wear, deformation, damage and/or leaking of lubricating oil in a bearing to make it impossible for the scroll fluid machine to exhibit expected performance and durability.
In order to overcome the problems, in JP7-42953B2 and JP10-26090A, a single fan is mounted to a driving shaft and external air is introduced from the surroundings of a housing with operation thereby cooling an eccentric axial portion of the driving shaft, its bearing and other surrounding members automatically.
JP7-42953B2 discloses a scroll fluid machine in FIGS. 4-7 in which, as cooling fluid sucked from the sucking hole 6 at one end of the frame 4 during operation goes to the discharge hole 16 at the other end of the frame 4, the fluid is heated gradually with various elements in the frame 4. Elements in the rear of the frame such as bearings 8 and 11 cannot be sufficiently cooled compared with the front elements, which is basically disadvantageous. In the reference, the motor is provided outside the frame 4 and there are no measures for cooling it positively.
JP10-26090A discloses a scroll fluid machine in which as shown in FIG. 2, after the motor 11 in the guide ring 16 is cooled with the sucked cooling wind 18, the cooling wind 17 is guided to the bearing 6, scroll compression chamber 7 etc. behind the motor 11. Thus, the temperature of the cooling wind 17 introduced to the bearing 6 is already raised considerably making it difficult to cool the elements behind the motor 11.
In order to solve such disadvantages, US2004/0241030A1 is suggested. To the driving shaft 8 driven by the motor 17, the cooling fans 16,15 are mounted in front of and behind the engaging portion of the fixed and orbiting scrolls 4c and 5. With operation, external cooling air is sucked via the through holes of the front and rear ends of the housing 1 by the cooling fans 16, 15, introducing external air over the broad area in the housing 1.
Each part of the scroll fluid machine is uniformly cooled, but the two cooling fans increase the whole size, weight and cost. And consumed electricity is increased as well as noise from the cooling fans. In the US Patent publication, there are no measures for cooling the driving motor positively.